Haze Season and Your Scalp: What Research Shows About Fine Particles and Skin, and How to Wash Through It

In most years, typically between August and October, the haze returns: the light over the Klang Valley turns flat and the air carries a faint smell of smoke. Most people think first of their lungs and eyes, and rightly so. Skin is the other surface that meets the air all day, and the scalp is skin.

What the haze carries, what it has been shown to do to skin, and what is worth adjusting in your washing during those weeks are three separate questions, and the answers are calmer than the headlines.

What is PM2.5, and where does the haze come from?

PM2.5 is shorthand for particulate matter 2.5 micrometres across or smaller: particles a small fraction of the width of a single hair, fine enough to stay suspended in the air for long periods. Everyday sources such as traffic add to them all year round.

In the dry season, a different source dominates. Haze episodes recur in most years, typically between August and October, mainly from peat and forest fires in Sumatra and Kalimantan, with smoke carried by seasonal winds. They tend to be worse in El Niño years.

When you check the air, note which scale you are reading. Malaysia’s Department of Environment reports its own Air Pollutant Index (API); some phone apps use the US Air Quality Index. The two are different scales, so a number from one cannot be compared with a number from the other.

Fine particles settle on every exposed surface. On the scalp they meet sweat and sebum, the oil that the scalp produces in greater concentration than almost anywhere else on the body, as your scalp is skin explains.

What do fine particles do to skin in human studies?

The most useful evidence comes from large human studies, and two stand out.

Singapore, the closest tropical evidence. A nationwide time-series study (Mailepessov and colleagues, 2024) analysed 1,440,844 outpatient consultations for atopic dermatitis (eczema). In weeks when PM2.5 reached the 90th percentile (24.4 µg/m³), consultations ran about 10 per cent higher than in a median week (relative risk 1.10, 95% confidence interval 1.01 to 1.19). Three details matter. The comparison sets a high week against a median week, rather than against clean air. The lower bound of 1.01 sits only just above no effect. And 24.4 µg/m³ is a moderate level, far from a severe haze reading. The study measured skin consultations and says nothing about the scalp or hair.

The UK, a large long-term cohort. In a prospective UK cohort (Chen and colleagues, 2024), researchers followed 193,995 adults, of whom 3,363 developed late-onset seborrhoeic dermatitis, the inflamed, flaking condition that often affects the scalp. People in the most polluted areas, the top quarter of long-term exposure, had an 11 to 22 per cent higher hazard than those in the lowest quarter, across several pollutants: about 11 per cent for PM2.5, 15 per cent for PM10 and 22 per cent for nitrogen dioxide, which is a gas rather than a particle. This is an association in a European population breathing ordinary urban air rather than haze smoke, and it does not show that pollution caused the condition.

What neither study shows matters as much. No study has yet looked at haze, skin and scalp in Malaysia, and none has examined peat-fire smoke specifically. No human study has shown that haze causes ordinary dandruff. And neither of these studies measured hair. The separate question of pollution and thinning is answered, with its own limits, in what the evidence says about pollution and thinning.

Why does the scalp deserve attention in haze weeks?

Because of what it already carries. Fine particles settle on the scalp and mix with sweat and oil, and in Malaysia’s heat that build-up is a reason to cleanse thoroughly. Hair also holds the mixture against the skin for longer than it would sit on an open cheek or forearm. None of this calls for alarm. It is the same logic as washing your face after a day outdoors in a smoky city.

How should you wash your scalp during haze season?

The adjustments are modest, and most of them are habits a careful routine already includes.

Two points deserve emphasis. Thoroughness here means a good lather and a long rinse. Scrubbing harder disturbs the skin barrier, which is the opposite of what a hazy week calls for. And frequency should still follow condition: a day spent in an air-conditioned office may not change your routine at all. For a fuller guide to frequency, see how often to wash your hair in Malaysia; for the routine step by step, see a practical home scalp-care routine.

When should you have your scalp looked at?

Haze weeks can coincide with an itchy or flaky spell, and it is tempting to blame the air. Seek medical assessment for redness or itching that does not settle with gentle washing, thick or greasy scale, pain, weeping, crusting, or any change in density that continues. Flakes and oiliness that cycle back are common in Malaysia and are covered in oily scalp and dandruff in Malaysia.

Conclusion: clean, gentle and consistent through the haze weeks

The evidence that fine particles affect skin is real but measured: associations from large human studies, none of them Malaysian and none of them about hair. The sensible response is equally measured. Wash after time outdoors, keep the water comfortable and the touch light, rinse well, and let the scalp tell you when the routine has gone too far.

Sources and further reading

• Mailepessov et al. (2024), Scientific Reports: ambient air pollution and skin consultations in Singapore, 1,440,844 consultations
• Chen et al. (2024), Clinical and Experimental Dermatology: air pollution and new skin diagnoses in a UK cohort of 193,995 adults
• Your scalp is skin: what that changes every time you wash
• Does air pollution cause hair thinning? What the evidence shows
• How often should you wash your hair in Malaysia?
• A practical home scalp-care routine
• Oily scalp and dandruff in Malaysia